Regional Irrigation Office 15 shall have the duties as follows:1. Implementation of water management for agriculture, domestic consumption,industry,water transportation, energy, and ecosystem conservation
2. Control and construction of small and medium scale irrigation project, royal project and other project as assigned by the Department
3. Planning, control, and evaluation of water management
4. Operation< maintenance and rehabilitation of irrigation structure; dam safety and appurtenant structures
5. Encouragement of farmer participation in water resources management; strengthening of water user organization
6. Prevention of damage caused by water
7. Studies and preparation of preliminary report; survey and design for irrigation project and other project in the river basin area as assigned by the Department
8. Control and supervision of state property land use as responsibility of the Department, irrigation waterway, and asset management of the Department
9. Integration of plans and strategies in cooperation with provincial agencies and other releated government agencies
10. Consulting in operation and maintenance of irrigation structures and transferred tasks
11. Cooperation with or supporting the operation of other offices and divisions as assigned by the Department

Responsible Area under Regional Irrigation Office 15
Regional Irrigation office 15 under the Royal Irrigation Department is assigned to solve water problems and implement irrigation works in 5 province of the middle southern region, consisting of Nakhon Si Thammarat, SuratThani, PhangNga, Krabi and Phuket, totaling responsible area of 21,793,216 rai, begin an irrigated area of 950,000 rai in 4 major river basin e.g. South-East Coast, Western Cost, tapi and Songkhla Lake River Basins.
Water Resources Development Project under Regional Irrigation Office 15 consists of 3 large scsle irrigation projects, 39 medium scale irrigation project, 501 small scale irrigation project and 33 other projects, totaling storagecapacity of 5,899.90 MCM. And beneficial area of approximately 100,000 rai.